This invention generally relates to boiler cleaning. More specifically, the invention relates to a retracting sootblower having a mechanism for articulating the sootblower and lance tube so that the lance tube can be inserted over multiple insertion axes through a single access port in a boiler.
Sootblowers are used to project a stream of blowing medium, such as water, air, or steam, against the heat transfer surfaces of the tube bank located within the boiler. The blowing medium is used to dislodge various combustion byproducts, including slag and ash, which become deposited on the heat transfer surfaces. If the encrustations are not removed, boiler efficiency significantly decreases. By using the blowing medium to dislodge the encrustations, the thermal and mechanical shock provided by the medium fractures the encrustations, breaking them free, and dislodges them from the heat transfer surfaces. Through effective and consistent sootblowing, the efficiency of the boiler can be maintained.
One particular category of sootblower is the retractable sootblower. A retractable sootblower is located outside of the boiler and its lance tube is periodically advanced into and withdrawn from the boiler to perform cleaning. One or more nozzles are located on the end of the lance tube and project jets of the blowing medium. While being inserted and retracted, the lance tube is rotated so that the jets trace helical paths across the heat transfer surfaces.
Current retractable sootblowers insert and withdraw the lance tube over a generally straight, horizontal line of travel. The nozzles installed on the end of the lance tube therefore define a cylindrical area within the boiler tube where effective cleaning will be performed. Invariably, some areas of the boiler tube bank are less than adequately cleaned or not cleaned at all because of the lance tube's fixed line of travel. Additionally, a large number of sootblowers are needed to adequately clean the tube bank.
For example, in a best case situation, an array of sootblowers is installed so that the area cleaned by one sootblower slightly overlaps the area cleaned by an adjacent sootblower. More specifically, when sootblowers are installed in a rectangular array (one sootblower located in each corner of the rectangle), a diamond shaped area in the center of the rectangle receives poor cleaning coverage. More commonly, the cleaned areas of adjacent sootblowers do not overlap and an even more substantial area of the boiler tubes is inadequately cleaned.
Previously, sootblowers have been proposed where the entire frame of the sootblower is vertically and horizontally moved so that the sootblower can be inserted through different access ports in the boiler wall to effect cleaning in different areas of the tube bank with a single sootblower. Additionally, sootblowers have been constructed where the lance tube itself is flexible and a steering member is incorporated so as to redirect the lance tube after being inserted a certain distance in the tube bank.
Another cleaning device is a flue blower. These devices are designed so that their lance is pointed within a flue and then turned on to effectuate cleaning within the flue. Some flue blowers can be manipulated to point at multiple flues. These systems are manual systems which require the operator to position the lance tube at the desired location, turn on the blowing medium, and, in limited circumstances, rotate the lance. They are not intended to be inserted or retracted during cleaning.
Lacking in the prior art is a retractable sootblower which is capable of pivoting about an axis so that the lance tube can be inserted and retracted along multiple axes, inclinations or orientations while being repeatably inserted and withdrawn through the same access port in the boiler wall.
With these limitations in mind, it is an object of the present invention to provide a retractable sootblower adapted to pivot so that the lance tube can be inserted and retracted along multiple insertion axes thereby providing enhanced cleaning of the boiler tube banks.
Another object of this invention is to provide a sootblower system where the lance tube can be inserted through a single access port, but over different insertion axes.
It is also an object of this invention to provide a sootblower which is capable of being inserted and retracted along different axes on successive operating cycles of the system.
A further object of this invention is to provide a sootblower system where the lance tube can be inserted and the axis of insertion changed in the midst of the cleaning cycle.
Another object of the present invention is to provide a piping connection which allows the retractable sootblower to pivot while still utilizing rigid steam piping for supplying the blowing medium.
In achieving the above and other objects, the present invention provides a retractable sootblower which is articulable so that the lance tube can be inserted into and retracted from within a boiler over multiple insertion axes, but through a single or common access port. The sootblower according to the present invention includes an exteriorly located frame mounted adjacent to a wall box or access port in the boiler wall. A carriage assembly is supported by the frame and coupled to a lance tube which has at least one nozzle at its distal end. The lance tube generally defines the axis along which it will be inserted into and withdrawn from the interior of the boiler. As the lance is inserted, retracted or both, it is also rotated by the carriage assembly. A blowing medium is discharged through the nozzles of the lance so that the blowing medium traces a helical path as it is discharged. Since the blowing medium is ejected under significant pressure and at a cooler temperature than the boiler interior, the mechanical and thermal shock imparted by the jets causes the encrustations to fracture and dislodge from the heat exchanger surfaces.
If the lance tube can only be inserted along a single axis because it is fixed in position relative to the boiler, inevitably some portions of the heat exchanger surfaces will not receive adequate cleaning or will fail to be cleaned at all. This problem is alleviated by the present invention through the incorporation of a mechanism which causes the sootblower tube to pivot about a horizontal axis located generally adjacent to the boiler wall and the access port. Having this adjustability, the lance tube can be inserted along multiple axes, substantially increasing the cleaning coverage achievable with each sootblower.
Another advantage of the present invention is that while a substantial increase in the cleaning coverage is achieved, little change is actually needed to the design of the sootblower itself including the sootblower frame, carriage, feed tube and lance tube. The present invention therefore has the ability to be easily incorporated in retrofit applications. By incorporating the present invention in a boiler installation, a lesser number of sootblowers will be needed per boiler application. Obviously, significant cost benefits can be gained by reducing the actual required number of sootblowers. In all likelihood, this cost reduction will more than offset the cost of a single articulating sootblower according to this invention.
A portion of the mechanism which enables this articulation causes the outboard end of the sootblower frame to be raised or lowered depending on the desired lance tube orientation. The inboard end of the frame is mounted for rotation about a horizontal pivot axis. In one particular embodiment, a hydraulic actuator is manipulated by a controller to raise or lower the outboard end of the sootblower frame. Once the sootblower frame has been repositioned at the desired angular orientation, movement of the sootblower carriage assembly can be commenced.
Another feature of the present invention is a pivotable steam piping connection. Since the blowing medium is provided at high pressures, rigid piping remains necessary. In the disclosed embodiment of the piping connection, a supply tube is attached to the front end of the sootblower frame coincident with the pivot axis of the sootblower. The supply tube is connected to a feeder pipe which extends from the pivot, rearward along the frame toward the outboard end of the sootblower. The coupling permits rotary motion to occur between the supply pipe and the feeder pipe. At the outboard end, the feeder pipe is connected to the popper valve in a conventional manner.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.